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Axis2 – Message exchange pattern

In this Tutorial we are going to see the quick overview of SOAP message exchange patterns. Message Exchange PatternAll the SOAP messages carry the same structure, the ways in which they are used can be combined into a number of different “Message Exchange Patterns”(MEPs). The two major message exchange patterns are

In-Out

In-Only

In-Out : In this MEP, the client sends a SOAP message to the server, which process the message and sends a response back. This is probably the most commonly used MEP, and it is useful for task such as searching for information or submitting information in situation in where acknowledgement is important.In-Only: In this MEP, the client sends a message to the server without expecting a response. You may use this MEP for activities such as pinging a service to wake it up, reporting information for which you do not need an acknowledgement and so on.With in these two MEPs, there is several variables to consider:

Blocking versus Non-Blocking

Number of parameters

Blocking vs Non-Blocking : When the client sends a message, the application may wait to receive a response before moving on, or it may simply send a message and specifying callback action to be completed when the response is received.Number of Parameters : Ultimately, a message sent from a client to server is intended to execute a particular action. That action may not require any parameters, or it may require one or more parameters.These parameters must be encoded as part of the payload of the message.taking all the options into consideration, you can create virtually any MEP. For example, you can create an Out-Only system by reversing roles for the In-Only MEP.Apache Axis2 also includes support for less prominent MEPs, such as Robust-In-Only.